Method for etching a semiconductor device

ABSTRACT

Disclosed is a manufacturing method of a semiconductor device, in which etching of a silicon oxide film is performed using a gaseous phase including hydrofluoric acid. A hard mask made of a compound of Si with C or a compound of Si with N is used to perform etching of a silicon oxide film in a gaseous phase including hydrofluoric acid.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of manufacturing asemiconductor device, and more particularly to a method of manufacturinga semiconductor device in which silicon oxide films are etched using agaseous phase including hydrofluoric acid.

[0003] 2. Description of the Related Art

[0004] Hitherto, silicon oxide films have been etched using a liquidphase including hydrofluoric acid with a protective film being anorganic resist.

[0005] In the conventional etching method described above, etching isperformed in a liquid phase. Therefore, parts of the etching portion ofthe silicon oxide film remains unetched, as shown in FIG. 3A, due todust, bubbles, or the like existing in the liquid phase, thereby beingdifficult to finely process the silicon oxide film with the conventionaletching method.

[0006] Also, an etchant in a gaseous phase including hydrofluoric acidpermeates through an organic resist film, with the result that portionsmasked with the organic resist film are also etched as shown in FIG. 3B.This means that it is impossible to perform the etching usinghydrofluoric acid in a gaseous phase.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide a method ofmanufacturing a semiconductor device in which etching of silicon oxidefilm is performed using a gaseous phase including hydrofluoric acid.

[0008] The present invention is characterized in that when etching ofthe silicon oxide film is performed in a gaseous phase includinghydrofluoric acid, a hard mask made of a compound of Si with C or acompound of Si with N is used as an alternative to an organic resist byutilizing their properties of being impermeable to an etchant existingin the gaseous phase including the hydrofluoric acid.

[0009] The usage of such a hard mask made of a compound of Si with C ora compound of Si with N makes it possible to perform etching in agaseous phase including hydrofluoric acid. As a result, it becomespossible to finely process the silicon oxide film and to eliminateunetched part of an etching target portion of the silicon oxide filmresulting from dust, bubbles, or the like existing in an etchingatmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the accompanying drawings:

[0011]FIGS. 1A to 1F are cross-sectional views illustrating amanufacturing method of a semiconductor device in accordance with afirst embodiment of the present invention, in which steps of themanufacturing method being shown in order;

[0012]FIGS. 2A to 2C are cross-sectional views illustrating amanufacturing method of a semiconductor device in accordance with asecond embodiment of the present invention, in which steps of themanufacturing method being shown in order; and

[0013]FIGS. 3A and 3B are cross-sectional views illustrating an exampleof a conventional manufacturing method of a semiconductor device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] A first embodiment of the present invention will be describedbelow with reference to FIG. 1A to 1F.

[0015] As shown in FIG. 1A, a hard mask 3 is formed on a silicon oxidefilm 2 formed on a semiconductor substrate 1. The hard mask 3 is formedusing a film that has property of being etched by hydrofluoric acid at alower speed than the silicon oxide and being impermeable to a gaseousphase including hydrofluoric acid. For instance, an SiC film or an SiNfilm formed by chemical vapor deposition (CVD) is used as the hard mask3.

[0016] Next, as shown in FIG. 1B, a patterned resist film 4 is formed onthe hard mask 3 and etching of the hard mask 3 is performed. Then, asshown in FIG. 1C, etching of the silicon oxide film 2 is performed usingthe hard mask 3 in a gaseous phase 5 including the hydrofluoric acid.

[0017] Consequently, as shown in FIG. 11D, the silicon oxide film 2 canbe etched using the gaseous phase including the hydrofluoric acid. Theprocesses following the etching operation are performed under any one ofthe conditions shown in FIG. 1D to 1F. FIG. 1D shows a condition inwhich the resist film 4 is not peeled off, FIG. 1E shows a condition inwhich the resist film 4 is peeled off, but the hard mask 3 is left onthe silicon oxide 2 as an insulating film and a shock absorbing film,and FIG. 1F shows a condition in which the hard mask 3 as well as theresist film 4 are peeled off.

[0018] A second embodiment of the present invention will be describedbelow with reference to FIGS. 2A to 2C.

[0019] Similarly to the first embodiment, the hard mask 3 is formed onthe silicon oxide film 2. Then, the hard mask 3 is etched using theresist film 4 subjected to patterning.

[0020] Thereafter, as shown in FIG. 2A, the resist film 4 is peeled offand the etching of the silicon oxide film 2 is performed. The processesfollowing the etching operation are performed under any one of theconditions shown in FIGS. 2B and 2C. FIG. 2B shows a condition in whichthe hard mask 3 is left on the silicon oxide film 2, whereas FIG. 2Cshows a condition in which the hard mask 3 is peeled off.

[0021] As described above, according to the present invention, a hardmask is formed using a compound of Si with C or a compound of Si with N.The usage of the hard mask makes it possible to perform etching using agaseous phase in which the hydrofluoric acid is included. This solvesthe problem in that with the conventional etching method using a liquidphase including the hydrofluoric acid, part of an etching target portionremains unetched due to dust, bubbles, or the like existing in theliquid phase. That is, it becomes possible to finely perform etchingwithout leaving such unetched part.

What is claimed is:
 1. A method for etching a semiconductor device,comprising the steps of: forming a hard mask on the surface of a siliconoxide formed on a semiconductor substrate, forming a resist film on aportion of the surface of the hard mask, etching the had mask, andetching the silicon oxide using a gaseous phase including hydrofluoricacid.
 2. A method for etching a semiconductor device according to claim1, wherein the hard mask has a lower etching rate to the silicon oxidefilm.
 3. A method for etching a semiconductor device according to claim1, wherein the hard mask is formed using one of a compound of Si with Cand a compound of Si with N.